— We did not see him at the lecture yesterday— You him since I went to an international

问题补充：

— We did not see him at the lecture yesterday．

— You him, since I went to an international conference with him．

A. mustn’t have seen

B. can’t have seen

C. couldn’t see

D. needn’t have seen

答案：

A. mustn’t have seen

(答案→)B. can’t have seen

C. couldn’t see

D. needn’t have seen

解析：考查情态动词用法。can’t have seen不可能做了某事；needn’t have seen本不必做某事，实际上却做了；情态动词+have done表示对过去的虚拟；情态动词+动词原形，表示对现在情况的虚拟；句意：—昨天在演讲上没有看见你。—你不可能看见他。因为我和他去参加了一个网络会议。故B正确。表示对过去情况有把握的否定推测。故B正确。